Technological advancement in the electronics and computer fields is continually providing newer and better products and devices that enhance our daily lives. These enhancements can be found virtually everywhere in our personal as well as business lives. As our lives become more and more reliant upon such devices, the fault tolerance of these devices needs to become greater and greater. The fault tolerance of a system refers to how well it continues to operate in the face of one or more faults, errors, or failures of its various components.
One method used to improve the fault tolerance of certain devices is referred to generally as "redundancy". In a redundant system, some or all of the components are duplicated, providing a backup component in the event a failure occurs in a primary component. One example of such redundancy is in RAID (Redundant Arrays of Independent Disks) systems, where multiple disks are used to store the same information. Thus, if one of the disks fails, another can replace it. "Failure" of a device or component typically refers to the drive or component no longer providing at least one of its functions at an expected level of operation. As a further level of fault tolerance components may receive their power from separate power sources. By using separate power sources, if either a disk or its power source fails, then another disk and power source combination is able to take its place.
However, one problem encountered in redundant systems is that of notification. In a redundant system, it would be beneficial for either the user or an administrator to know when a primary system has failed and the backup is operating in its place. One way to do this is for the failed system to provide an indication (e.g., an alert light) that it has failed. However, such an indication is ineffective if the power to the component has failed (e.g., an alert light cannot be illuminated if there is no power to illuminate it).
A similar problem is encountered in systems that do not employ redundancy. A component of the system may fail due to a problem with its power supply or power distribution within the component. Again, it would be beneficial for either the user or a system administrator to know that the component has failed. However, providing an indication (e.g., an alert light) is ineffective if the failure prevents power from getting to the indicator.
The invention described below addresses these and other disadvantages of the prior art, providing improved redundant status indicators.